GMPhotography wrote:
It falls through other retaining rings. The EL Pro catches it so no need for a 55-52. I tried finding where this is mentioned but could not.
Understand now. Just wonder, will 49->52 and then blank 52 filter with retaining ring works? I understand PCX 5M is only around 50mm right?
wstam wrote:
Understand now. Just wonder, will 49->52 and then blank 52 filter with retaining ring works? I understand PCX 5M is only around 50mm right?
Proxar 0.5m for ZM18 is not my estimation but @candreyo@'s report.
I respect candreyo's experiment and ZM18 is not my own lens, but in theory Proxar (Meniscus) 0.5m seems be too strong. PCX 3m would work better. I will post simulated MTFs later.
Luckily Samuli's order includes 3m Optosigma. Looking forward to see Samuli's ZM18+PCX3m test.
Though Optosigma's 50mm diameter may be too small. I'm worrying mechanical vignetting.
And thank you for creating that wiki, Samuli!
Haruhiko
Here is my simulation result.
PCX 3m (e.g. SLB-50-3000PM) would be optimal for Zeiss ZM Distagon 18mm F4.
Lower left graph shows there is huge Field Curvature without filter, and the lower right graph shows resolution peaks well centered across frame, that means the FC is well corrected.
Correction of FC greatly contributes to corner sharpness when you focus on center (Upper two graphs).
Fred I had them. If not maybe get a small hacksaw so you get both at once lined up. Been thinking about that for you when you mentioned you did not. Or drill two small holes if you have a spanner
Fred Miranda wrote:
Guy,
Did your LPRO3 had the two nobs for rotation or you had to make them to removing the retention ring?
HaruhikoT wrote:
Here is my simulation result.
PCX 3m (e.g. SLB-50-3000PM) would be optimal for Zeiss ZM Distagon 18mm F4.
Lower left graph shows there is huge Field Curvature without filter, and the lower right graph shows resolution peaks well centered across frame, that means the FC is well corrected.
Correction of FC greatly contributes to corner sharpness when you focus on center (Upper two graphs).
Good thing about this is that with a weak 3m filter, probably there's no need to disassemble the ZM18 for removing shims. All adapters focusing a bit past infinity should work.
HaruhikoT wrote:
Here is my simulation result.
PCX 3m (e.g. SLB-50-3000PM) would be optimal for Zeiss ZM Distagon 18mm F4.
Lower left graph shows there is huge Field Curvature without filter, and the lower right graph shows resolution peaks well centered across frame, that means the FC is well corrected.
Correction of FC greatly contributes to corner sharpness when you focus on center (Upper two graphs).
Thanks, Haruhiko! I reached out to Brad at Sigma to see if it's possible to special order a PCX 3m with a 57mm diameter. I'll let everyone know what he says when I hear back.
Please do. I'm still really tempted to buy a used ZM 18. That give me 4 ZM lenses that have the same Zeiss look.
freaklikeme wrote:
Thanks, Haruhiko! I reached out to Brad at Sigma to see if it's possible to special order a PCX 3m with a 57mm diameter. I'll let everyone know what he says when I hear back.
Unfortunately, 0.5m was the filter that I found worked best from what I had available to try out. I have the 0.5, 1.0 and 2.0 Proxars and a 1500mm Planoconvex.
0.5m may not be the best filter for the ZM18 as Haruhiko mentions. I do find that a different filter could help us gain more with this lens, but not sure myself what filter would be the most optimum for this lens.
I did not have issues with vignetteing using the 0.5mm Proxar. I held the Proxar against the front of the lens using a 58mm lens adapter ring.
I am interested to see Samuli's results also 😁
If the 3000mm works really well for the ZM18, I may pull the trigger myself for one of them, along with a 5000mm for the 35mm Distagon ZM.
Proxar 0.5m for ZM18 is not my estimation but @candreyo@'s report.
I respect candreyo's experiment and ZM18 is not my own lens, but in theory Proxar (Meniscus) 0.5m seems be too strong. PCX 3m would work better. I will post simulated MTFs later.
Luckily Samuli's order includes 3m Optosigma. Looking forward to see Samuli's ZM18+PCX3m test.
Though Optosigma's 50mm diameter may be too small. I'm worrying mechanical vignetting.
And thank you for creating that wiki, Samuli!
candreyo wrote:
Unfortunately, 0.5m was the filter that I found worked best from what I had available to try out. I have the 0.5, 1.0 and 2.0 Proxars and a 1500mm Planoconvex.
0.5m may not be the best filter for the ZM18 as Haruhiko mentions. I do find that a different filter could help us gain more with this lens, but not sure myself what filter would be the most optimum for this lens.
I did not have issues with vignetteing using the 0.5mm Proxar. I held the Proxar against the front of the lens using a 58mm lens adapter ring.
I am interested to see Samuli's results also 😁
If the 3000mm works really well for the ZM18, I may pull the trigger myself for one of them, along with a 5000mm for the 35mm Distagon ZM.
Right now with the Hoya +1 closeup lens for my ZM 25. I have the Proxar 1 left over for something. Maybe Im crazy but the 35 takes the .5 the 25 takes the +1 you would think the 18 would take a +2. More field curvature as you get wider. What am I missing
GMPhotography wrote:
Right now with the Hoya +1 closeup lens for my ZM 25. I have the Proxar 1 left over for something. Maybe Im crazy but the 35 takes the .5 the 25 takes the +1 you would think the 18 would take a +2. More field curvature as you get wider. What am I missing
Well it's not just down to angle of view; it's a question of ray angle calculated from exit pupil position as well as FL; so there's no way to guess accurately just from fl or a sense of how much field curvature there is.
So if Haruhiko's simulations based on that data say 3m Optosigma, that's where I'd start...
GMPhotography wrote:
Right now with the Hoya +1 closeup lens for my ZM 25. I have the Proxar 1 left over for something. Maybe Im crazy but the 35 takes the .5 the 25 takes the +1 you would think the 18 would take a +2. More field curvature as you get wider. What am I missing
It's a difference in lens design and the resulting positions of the exit pupils. Your Biogon and my Elmarit 24 are closer to their true focal lengths (exit pupil to sensor) than the Distagons. So the 35 should take a lower amount of correction because its exit pupil is the farthest away from the sensor. The 18 is somewhere between the 35 and 25, apparently.
At least that's what I got out of the conversation in the first fifteen pages or so of this thread. I may be misinterpreting.
BastianK wrote:
Almost all rangefinder lenses look more or less good in the corners at f/8.0 (except for mainly some Biogons).
We are discussing options to get at least usable corners wide open.
Okay after another short test on the ZM 35mm 1.4 with my new setup at F4 my corners are killer good. Thats at least a 2 stop improvement.
Things get interesting with the ZM 25 with the Hoya +1 vs the Proxar +1. At 2.8 the Hoya has the slight edge in the corners and interestingly enough the mid range is better and slightly better contrast. Given I can use the hood with the Hoya is easier and just dropping it in a 46mm blank mount its the obvious choice. By F4 it all equals out
